Iron. 
found all the varieties susceptible of various degrees of 
carbonation : for the most part I have used chalk and 
charcoal for the reduction of the ore into carbonated crude 
iron. In the haematites variety, for 1 lb. avoirdupois I 
have commonly added 6 oz. dried chalk* and 3-4ths oz. 
of charcoal ; and for the spiinty blue ore also a similar 
mixture. From both of these I have obtained the rich- 
est sort of crude iron. In the manufactory, these varie- 
ties are always reckoned to produce the hardest and most 
infusible qualities of crude iron : when the metal is sub- 
sequently manufactured into bars, it is stated at different 
places to produce cold and hot short iron. 
The kidney ore will admit of a diminution of chalk, and 
a small addition of glass ; 1 lb. avoirdupois of this varie- 
ty will be accurately assayed with the addition of 5 oz. 
chalk, 1 oz. of glass, and 3-4ths oz. charcoal. The same 
proportion of mixtures will also accurately reduce the 
small pieces of this ore, commonly of a soft, greasy con- 
sistency, mixed with small fragments of the haematites 
and kidney, and will give out the iron which they contain 
super-carbonated. A mixture of this soft ore with kid- 
ney is preferred to the richer varieties at the iron manu- 
factories. The Lancashire ore chiefly consists of this 
compound, and the poorer in iron has always a decided 
preference given it at the blast furnace. 
The stratified iron ore of the island of Islay is of most 
difficult fusion when treated without any addition. It 
fuses into a blackish green ponderous mass, and, even 
exposed to the highest heats, lets fall but a small share of 
its iron. The quality thus obtained is in the highest degree 
oxygenated ; its fracture is partially crystallised in lines 
which converge towards the upper surface of the button, 
similar in crystallisation to the fracture of zinc. A re- 
gains thus obtained, when divested of its scoria, and pro- 
* Instead of chalk, pure limestone or marble might be used, T. G 
